Preheat oven to 375°F.

Season the chicken thighs with the Lipton onion soup mix and all-purpose seasoning.

Heat 1 tablespoon of olive oil in a large oven-safe skillet or baking dish over medium-high heat. Sear the chicken until browned on both sides. The chicken does not need to be fully cooked through at this stage. Remove and set aside.

Add the remaining olive oil to the pan along with the sliced onions. Sauté for about 3 minutes until softened and lightly caramelized. Deglaze the pan with a splash of cooking sherry wine, scraping up all the flavorful browned bits from the bottom.

Stir in the uncooked rice, spinach leaves, chicken stock, and a splash of heavy cream.

Nestle the chicken thighs back into the pan on top of the rice mixture. Spoon the onions over the chicken, then scatter the diced butter across the top.

Cover tightly with foil or a lid and bake for 20 minutes.

Uncover and continue baking for an additional 15 minutes until the rice is tender, the chicken is cooked through, and the top is golden around the edges.

Let rest for about 5 minutes before serving.